Sintered friction material

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a friction material, and more particularly, it relates to a friction material which is optimum for a sliding surface of a brake lining, a disc pad, a clutch facing or the like in a braking system of an automobile, rolling stock, an aircraft, an industrial machine or the like.
2. Description of the Prior Art
A friction material prepared by dispersing a base material in a binder of resin such as phenolic resin or epoxy resin, adding a friction conditioner as needed and binding and molding the mixture under heat and pressure is known for use as a friction material in the aforementioned braking system.
The friction coefficient of such a friction material is generally reduced as the temperature is increased. When an automobile continuously goes down descents or the like, therefore, the braking performance is remarkably reduced through so-called fading as the friction material becomes frictionally heated. To this end, a friction material employed under a high load condition is prepared from a sintered alloy based on a metal such as copper with addition of a friction conditioner such as graphite or ceramics in recent years.
However, some conventional friction material of a sintered alloy (hereinafter referred to as a sintered friction material) is insufficient in lubricity and remarkably abrades the counterpart although the friction material itself is less abraded. Another conventional friction material is remarkably abraded itself, although it abrades the counterpart to a larger degree. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
Still another conventional sintered friction material is insufficient in lubricity and remarkably abrades the counterpart although it exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although it abrades the counterpart to a larger degree. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in material strength although the same exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although the same is sufficient in material strength. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in judder resistance or chatter resistance although the friction material itself is less abraded. A further friction material is remarkably abraded itself although the same is sufficient in judder resistance. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in creak resistance or squealing resistance although the same exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although the same is sufficient in creak resistance. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sintered friction material compatibly improving its abrasion resistance and suppressing abrasion of the counterpart.
Another object of the present invention is to provide a sintered friction material compatibly attaining a high friction coefficient and suppressing abrasion of the counterpart.
Still another object of the present invention is to provide a sintered friction material compatibly attaining both a high friction coefficient and excellent material strength.
A further object of the present invention is to provide a sintered friction material compatibly attaining both abrasion resistance and judder resistance.
A further object of the present invention is to provide a sintered friction material compatibly attaining both a high friction coefficient and excellent creak resistance.
The sintered friction material according to the present invention has a matrix of a copper-system metal and contains a specific additive, graphite and potassium titanate as friction conditioners, while the specific additive consists of at least one material selected from a group consisting of zirconium oxide, silica, dolomite, orthoclase and magnesium oxide.
The matrix of a copper-system metal, having excellent expandability and high hot conductivity, can stabilize the friction coefficient and disperse heat spots, while improving the friction coefficient through adhesion to the counterpart. The graphite improves the abrasion resistance of the friction material, while the potassium titanate suppresses adhesion to the counterpart for inhibiting abrasion of the counterpart and matches with the matrix material for maintaining the material strength.
When prepared from any of zirconium oxide, silica and dolomite (CaCO.sub.3 .multidot.MgCO.sub.3), the specific additive improves the frictional force by removing an oxide film or the like adhering to the surface of the counterpart. When prepared from orthoclase K.sub.2 O.multidot.Al.sub.2 O.sub.3 .multidot.6SiO.sub.2), the specific additive has proper hardness and small attackability to the counterpart, and improves the judder resistance. When prepared from magnesium oxide, the specific additive improves the creak resistance by improving the damping property of the friction material.
In order to sufficiently attain the aforementioned effects, the sintered friction material preferably contains the specific additive, the graphite and the potassium titanate by 1 to 15%, 10 to 50% and 5 to 30% in volume ratio respectively.
The frictional force is insufficiently improved if the volume ratio of zirconium oxide is smaller than 1%, while the effect of suppressing abrasion of the counterpart is reduced due to removal of the counterpart if this volume ratio exceeds 15%. Zircon (ZrSiO.sub.4) may be employed in place of or along with zirconium oxide.
The frictional force is insufficiently improved if the volume ratio of silica is smaller than 1%, while the effect of suppressing abrasion of the counterpart is reduced due to removal of the counterpart if this volume ratio exceeds 15%. Silica is preferably prepared from at least one of crystal silica obtained by crushing natural ore as such, fused silica obtained by fusing and vitrifying ore at a high temperature of at least 1800.degree. C. and thereafter crushing the same, and industrially synthesized amorphous silica.
The frictional force is insufficiently improved if the volume ratio of dolomite is smaller than 1%, while the matrix is inhibited from sintering and the material strength is reduced if this volume ratio exceeds 15%.
The judder resistance is insufficiently improved if the volume ratio of orthoclase is smaller than 1%, while the matrix is inhibited from sintering and the material strength is reduced if this volume ratio exceeds 15%.
The creak resistance is insufficient if the volume ratio of magnesium oxide is smaller than 1%, while the matrix is inhibited from sintering and the material strength is reduced if this volume ratio exceeds 15%.
The abrasion resistance of the friction material is insufficiently improved if the volume ratio of graphite is smaller than 10%, while the material strength is remarkably reduced to deteriorate the abrasion resistance if this volume ratio exceeds 50%.
The effect of suppressing abrasion of the counterpart is insufficient and the effect of maintaining the material strength is not attained if the volume ratio of potassium titanate is smaller than 5%, while the effect of maintaining the material strength is saturated to result in reduction of the material strength and deterioration of the abrasion resistance if this volume ratio exceeds 30%.
While potassium titanate is a compound expressed in a general formula K.sub.2 O.multidot.nTiO.sub.2, a practical friction conditioner is obtained when n is equal to 2, 4, 6 or 8. Potassium hexatitanate is particularly preferable. Alternatively, a composite material prepared by granularly sintering potassium titanate and calcium titanate may be employed.
The grain size of zirconium oxide is suitably in the range of 0.5 to 200 .mu.m. If the grain size is smaller than the lower limit of this range, the zirconium oxide cannot remove an oxide film adhering to the surface of the counterpart and no improvement of the frictional force is attained. If the grain size exceeds the upper limit of the above range, on the other hand, the zirconium oxide removes not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, and hence the effect of suppressing abrasion of the counterpart is deteriorated.
The grain size of silica is suitably in the range of 0.5 to 200 .mu.m. If the grain size is smaller than the lower limit of this range, the silica cannot remove an oxide film adhering to the surface of the counterpart and no improvement of the frictional force is attained. If the grain size exceeds the upper limit of the above range, on the other hand, the silica removes not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, and hence the effect of suppressing abrasion of the counterpart is deteriorated.
The grain size of dolomite is suitably in the range of 0.5 to 200 .mu.m. If the grain size is smaller than the lower limit of this range, the dolomite cannot remove an oxide film adhering to the surface of the counterpart and no improvement of frictional force is attained. If the grain size of the dolomite exceeds the upper limit of the above range, on the other hand, the matrix is inhibited from sintering and the material strength is reduced. Dolomite is preferably prepared either by crushing natural ore as such or baking the same.
The grain size of orthoclase is suitably in the range of 0.5 to 200 .mu.m. If the grain size of the orthoclase is smaller than the lower limit of this range, the matrix is inhibited from sintering and the material strength is reduced. If the grain size of the orthoclase exceeds the upper limit of the above range, on the other hand, judder resistance is insufficiently improved.
The grain size of magnesium oxide is suitably in the range of 0.5 to 200 .mu.m. If the grain size of the magnesium oxide is smaller than the lower limit of this range, the matrix is inhibited from sintering and the material strength is reduced. If the grain size of the magnesium oxide exceeds the upper limit of the above range, on the other hand, no improvement of the damping property of the friction material is attained and the creak resistance is insufficiently improved.
The grain size of graphite is suitably in the range of 10 to 1000 .mu.m. If the grain size of the graphite is smaller than the lower limit of this range, the matrix is inhibited from sintering and the material strength is reduced to deteriorate the abrasion resistance of the friction material. If the grain size exceeds the upper limit of the above range, on the other hand, segregation of the graphite is so remarkable that it is difficult to ensure a homogeneously dispersed state.
The form of potassium titanate is preferably at least one of whiskery, platy (or plate-like) and spherical forms. In particular, spherical potassium titanate is more preferable as compared with whiskery and platy ones in the following points:
(1) The spherical potassium titanate less reduces the material strength as compared with the whiskery and platy ones.
(2) The spherical potassium titanate is hardly crushed but homogeneously dispersed as such when mixed into the material powder.
(3) The spherical potassium titanate is less segregated due to excellent flowability of the mixed powder when introduced into a mold.
(4) The spherical potassium titanate has a remarkable effect of improving the damping property of the sintered body and suppressing creaking due to internal friction of spherical grains.
A further friction conditioner, a preservative and/or a lubricant may be added to the sintered friction material according to the present invention in a proper amount as needed as a matter of course. For example, barium sulfate, magnetite, fluorite and/or molybdenum disulfate may be added to the inventive sintered friction material.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Examples of the present invention are now described.

(TEST EXAMPLE 1)
Mixed powder materials were prepared by blending matrices, zirconium oxide, graphite and potassium titanate in the ratios shown in Table 1, molded into green compacts under a pressure of 2 to 5 tons/cm.sup.2 and thereafter sintered in an N.sub.2 atmosphere at 750.degree. C. for 20 to 90 minutes, thereby preparing samples Nos. 1 to 31 of sintered friction materials.
TABLE 1__________________________________________________________________________ Matrix Potassium Titanate Total Zirconium Oxide Graphite Total Ratio Ratio Ratio RatioSample (Vol. (Vol. Grain Size (Vol. Grain Size (Vol.No. Classification Cu Sn Ni Al %) %) (.mu.m) %) (.mu.m) Whiskery Platy Spherical %)__________________________________________________________________________1 inventive 34 5 0 0 39 14 0.5.about.200 30 200.about.400 0 0 17 172 inventive 33 5 0 0 38 2 0.5.about.200 45 200.about.400 0 0 15 153 inventive 33 5 0 0 38 8 0.5.about.200 24 200.about.400 0 0 30 304 inventive 33 5 0 0 38 14 0.5.about.200 20 200.about.400 0 0 28 285 inventive 37.5 5.5 0 0 43 14 0.5.about.200 15 200.about.400 0 0 28 286 inventive 36 5 0 0 41 14 0.5.about.200 40 200.about.400 0 0 5 57 inventive 36 5 0 0 41 14 0.5.about.200 30 200.about.400 0 0 15 158 inventive 33 5 0 0 38 8 0.5.about.200 40 200.about.400 0 0 14 149 inventive 33 5 0 0 38 8 0.5.about.200 40 200.about.400 0 14 0 1410 inventive 33 5 0 0 38 8 0.5.about.200 40 200.about.400 14 0 0 1411 inventive 33 5 0 0 38 8 0.5.about.200 40 200.about.400 0 7 7 1412 inventive 33 5 0 0 38 8 0.5.about.200 40 200.about.400 7 0 7 1413 comparative 33 5 0 0 38 0.5 0.5.about.200 43 200.about.400 0 0 18.5 18.514 comparative 33 5 0 0 38 18 0.5.about.200 33 200.about.400 0 0 11 1115 comparative 48 7 0 0 55 15 0.5.about.200 5 200.about.400 0 0 25 2516 comparative 32 5 0 0 37 2 0.5.about.200 55 200.about.400 0 0 6 617 comparative 33 5 0 0 38 15 0.5.about.200 44 200.about.400 0 0 3 318 comparative 33 5 0 0 38 5 0.5.about.200 25 200.about.400 0 0 32 3219 comparative 33 5 0 0 38 8 0.01.about.0.4 40 200.about.400 0 0 14 1420 comparative 33 5 0 0 38 8 220.about.400 40 200.about.400 0 0 14 1421 comparative 33 5 0 0 38 8 0.5.about.200 40 0.1.about.8 0 0 14 1422 comparative 33 5 0 0 38 8 0.5.about.200 40 1200.about.2000 0 0 14 1423 inventive 24 3 11 0 38 8 0.5.about.200 40 200.about.400 0 0 14 1424 inventive 24 3 11 0 38 8 0.5.about.200 40 200.about.400 0 14 0 1425 inventive 24 3 11 0 38 8 0.5-200 40 200.about.400 14 0 0 1426 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 0 0 14 1427 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 0 14 0 1428 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 14 0 0 1429 comparative 40 6 0 0 46 14 0.5.about.200 40 200.about.400 0 0 0 030 comparative 27 4 15 0 46 14 0.5.about.200 40 200.about.400 0 0 0 031 comparative 27 4 12 3 46 14 0.5.about.200 40 200.about.400 0 0 0 0__________________________________________________________________________
A general performance test was made on the samples in accordance with the JASO C406-82 passenger car braking device dynamometer test method. The ranges of friction coefficients were measured at initial braking speeds of 50 km/h and 100 km/h and deceleration of 0.1 to 0.9 G in a second effectiveness test. Abrasion loss values of the samples and the counterparts of cast iron were measured before and after the general performance test. Table 2 shows the results. Referring to Tables 1 and 2, the samples Nos. 1 to 12 and 23 to 28 are inventive samples, and the samples Nos. 13 to 22 and Nos. 29 to 31 are comparative samples. In the columns of "Classification", "inventive" and "comparative" indicate the inventive and comparative samples respectively.
TABLE 2______________________________________ Abra- AbrasionSam- Friction sion Loss ofple Classi- Coeffi- Loss Counter- Appearance afterNo. fication cient (mm) part (mm) Friction Test______________________________________1 inventive 0.40.about.0.48 0.12 0.05 excellent with neither chipping nor cracking2 inventive 0.33.about.0.40 0.10 0.05 excellent with neither chipping nor cracking3 inventive 0.35.about.0.45 0.13 0.04 excellent with neither chipping nor cracking4 inventive 0.40.about.0.48 0.14 0.04 excellent with neither chipping nor cracking5 inventive 0.40.about.0.48 0.15 0.04 excellent with neither chipping nor cracking6 inventive 0.40.about.0.48 0.10 0.09 excellent with neither chipping nor cracking7 inventive 0.40.about.0.48 0.12 0.05 excellent with neither chipping nor cracking8 inventive 0.38.about.0.45 0.10 0.05 excellent with neither chipping nor cracking9 inventive 0.35.about.0.45 0.10 0.05 excellent with neither chipping nor cracking10 inventive 0.35.about.0.45 0.10 0.05 excellent with neither chipping nor cracking11 inventive 0.37.about.0.45 0.10 0.05 excellent with neither chipping nor cracking12 inventive 0.37.about.0.45 0.10 0.05 excellent with neither chipping nor cracking13 compar- 0.15.about.0.25 0.25 0.06 excellent with neither ative chipping nor cracking14 compar- 0.35.about.0.50 0.22 0.30 corner chipped ative15 compar- 0.35.about.0.45 0.50 0.09 excellent with neither ative chipping nor cracking16 compar- 0.30.about.0.40 0.45 0.08 corner chipped ative17 compar- 0.35.about.0.45 0.20 0.30 corner chipped ative18 compar- 0.35.about.0.45 0.45 0.25 corner chipped ative19 compar- 0.15.about.0.25 0.25 0.09 excellent with neither ative chipping nor cracking20 compar- 0.25.about.0.45 0.20 0.30 corner chipped ative21 compar- 0.32.about.0.40 0.30 0.09 corner chipped ative22 compar- 0.25.about.0.50 0.35 0.18 corner chipped ative23 inventive 0.36.about.0.47 0.12 0.05 excellent with neither chipping nor cracking24 inventive 0.36.about.0.47 0.12 0.06 excellent with neither chipping nor cracking25 inventive 0.36.about.0.47 0.12 0.06 excellent with neither chipping nor cracking26 inventive 0.38.about.0.48 0.13 0.05 excellent with neither chipping nor cracking27 inventive 0.38.about.0.48 0.13 0.06 excellent with neither chipping nor cracking28 inventive 0.38.about.0.48 0.13 0.06 excellent with neither chipping nor cracking29 compar- 0.35.about.0.45 0.30 0.50 corner chipped ative30 compar- 0.36.about.0.47 0.32 0.52 corner chipped ative31 compar- 0.38.about.0.48 0.35 0.55 corner chipped ative______________________________________
As understood from Table 2, the samples Nos. 1 to 12 having matrices of copper and tin exhibited high friction coefficients and small abrasion loss values of the friction materials and the counterparts. It is also understood that the samples Nos. 1 to 12 were sufficient in strength with neither chipping nor cracking on the appearances after the test.
On the other hand, the samples Nos. 13 to 22, similarly having matrices of copper and tin, were insufficient as friction materials as described below:
The sample No. 13 containing zirconium oxide in a ratio smaller than those of the remaining samples exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 14 containing zirconium oxide in a high ratio removed not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, which was remarkably abraded.
The sample No. 15 containing graphite in a ratio smaller than those of the remaining samples exhibited high abrasion loss. The sample No. 16 containing graphite in a high ratio was remarkably reduced in material strength and increased in abrasion loss.
The sample No. 17 containing potassium titanate in a ratio smaller than those of the remaining samples remarkably abraded the counterpart and had an insufficient effect of suppressing abrasion of the counterpart. The sample No. 18 containing potassium titanate in a ratio larger than those of the remaining samples was reduced in material strength and increased in abrasion loss.
The sample No. 19 containing zirconium oxide in a grain size smaller than those of the remaining samples was incapable of removing an oxide film or the like adhering to the surface of the counterpart and exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 20 containing zirconium oxide in a grain size larger than those of the remaining samples removed not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, which was remarkably abraded.
The sample No. 21 containing graphite in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and deteriorated in abrasion resistance. The sample No. 22 containing graphite in a grain size larger than those of the remaining samples was incapable of ensuring a homogeneous dispersed state and obtaining a stable friction coefficient due to remarkable segregation of graphite, and increased in abrasion loss.
The samples Nos. 23 to 25 having matrices of copper, tin and nickel exhibited higher friction coefficients as compared with those of the samples Nos. 1 to 12, with small abrasion loss of the friction materials and the counterparts. Further, the samples Nos. 23 to 25 were sufficient in strength for serving as friction materials with neither chipping nor cracking on the appearances after the test.
The samples Nos. 26 to 28 having matrices of copper, tin, nickel and aluminum exhibited higher friction coefficients as compared with those of the samples Nos. 23 and 25, with small abrasion loss of the friction materials and the counterparts. Further, the samples Nos. 26 to 28 were sufficient in strength for serving as friction materials with neither chipping nor cracking on the appearances after the test. On the other hand, the samples Nos. 29 to 31 of conventional sintered friction materials containing no potassium titanate exhibited insufficient effects of suppressing abrasion of the counterparts with remarkable abrasion loss of the counterparts due to the absence of potassium titanate.
(TEST EXAMPLE 2)
Mixed powder materials were prepared by blending matrices, silica, graphite and potassium titanate in the ratios shown in Table 3, molded into green compacts under a pressure of 2 to 5 tons/cm.sup.2 and thereafter sintered in an N.sub.2 atmosphere at 750.degree. C. for 20 to 90 minutes, thereby preparing samples Nos. 101 to 125 of sintered friction materials.
TABLE 3__________________________________________________________________________ Matrix Potassium Titanate Total Silica Graphite Total Ratio Ratio Ratio RatioSample (Vol. (Vol. Grain Size (Vol. Grain Size (Vol.No. Classification Cu Sn Ni Al %) %) (.mu.m) %) (.mu.m) Whiskery Platy Spherical %)__________________________________________________________________________101 inventive 23 3 10 2 38 14 0.5.about.200 30 200.about.400 0 0 18 18102 inventive 23 3 10 2 38 2 0.5.about.200 45 200.about.400 0 0 15 15103 inventive 23 3 10 2 38 8 0.5.about.200 26 200.about.400 0 0 28 28104 inventive 23 3 10 2 38 14 0.5.about.200 20 200.about.400 0 0 28 28105 inventive 26 3.4 11.3 2.3 43 14 0.5.about.200 15 200.about.400 0 0 28 28106 inventive 24.8 3.2 10.8 2.2 41 14 0.5.about.200 40 200.about.400 0 0 5 5107 inventive 24.8 3.2 10.8 2.2 41 14 0.5.about.200 30 200.about.400 0 0 15 15108 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 0 0 14 14109 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 0 14 0 14110 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 14 0 0 14111 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 0 7 7 14112 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.400 7 0 7 14113 comparative 23 3 10 2 38 0.5 0.5.about.200 43 200.about.400 0 0 18.5 18.5114 comparative 23 3 10 2 38 18 0.5.about.200 33 200.about.400 0 0 11 11115 comparative 33.3 4.3 14.5 2.9 55 15 0.5.about.200 5 200.about.400 0 0 25 25116 comparative 22.4 2.9 9.7 2.0 37 2 0.5.about.200 55 200.about.400 0 0 6 6117 comparative 23 3 10 2 38 15 0.5.about.200 44 200.about.400 0 0 3 3118 comparative 23 3 10 2 38 5 0.5.about.200 25 200.about.400 0 0 32 32119 comparative 23 3 10 2 38 8 0.01.about.0.4 40 200.about.400 0 0 14 14120 comparative 23 3 10 2 38 8 220.about.400 40 200.about.400 0 0 14 14121 comparative 23 3 10 2 38 8 0.5.about.200 40 0.1.about.8 0 0 14 14122 comparative 23 3 10 2 38 8 0.5.about.200 40 1200.about.2000 0 0 14 14123 comparative 27 4 12 3 46 14 0.5.about.200 40 200.about.400 0 0 0 0124 comparative 26 3.4 11.3 2.3 43 14 0.5.about.200 43 200.about.400 0 0 0 0125 comparative 24.8 3.2 10.8 2.2 41 14 0.5.about.200 45 200.about.400 0 0 0 0__________________________________________________________________________
A general performance test was carried out on the samples in accordance with the JASO C406-82 passenger car braking device dynamometer test method. The ranges of friction coefficients were measured at initial braking speeds of 50 km/h and 100 km/h and deceleration of 0.1 to 0.9 G in a second effectiveness test. Abrasion loss values of the samples and the counterparts of cast iron were measured before and after the general performance test. Table 4 shows the results. Referring to Tables 3 and 4, the samples Nos. 101 to 112 are inventive samples, and the samples Nos. 113 to 125 are comparative samples. In the columns of "Classification", "inventive" and "comparative" indicate the inventive and comparative samples respectively.
TABLE 4______________________________________ Abrasion Abrasion LossSample Friction Loss of CounterpartNo. Classification Coefficient (mm) (mm)______________________________________101 inventive 0.48.about.0.55 0.12 0.06102 inventive 0.45.about.0.50 0.09 0.05103 inventive 0.46.about.0.53 0.13 0.04104 inventive 0.48.about.0.55 0.14 0.04105 inventive 0.48.about.0.56 0.15 0.04106 inventive 0.48.about.0.54 0.10 0.09107 inventive 0.48.about.0.54 0.12 0.05108 inventive 0.46.about.0.52 0.10 0.05109 inventive 0.46.about.0.52 0.10 0.05110 inventive 0.46.about.0.52 0.10 0.05111 inventive 0.46.about.0.52 0.10 0.05112 inventive 0.46.about.0.52 0.10 0.05113 comparative 0.20.about.0.28 0.25 0.06114 comparative 0.45.about.0.55 0.22 0.45115 comparative 0.40.about.0.48 0.50 0.09116 comparative 0.30.about.0.40 0.45 0.08117 comparative 0.45.about.0.50 0.20 0.30118 comparative 0.46.about.0.53 0.45 0.25119 comparative 0.18.about.0.28 0.25 0.09120 comparative 0.45.about.0.58 0.20 0.30121 comparative 0.46.about.0.53 0.40 0.09122 comparative 0.35.about.0.58 0.35 0.18123 comparative 0.48.about.0.58 0.30 0.55124 comparative 0.48.about.0.56 0.26 0.52125 comparative 0.48.about.0.54 0.22 0.50______________________________________
As understood from Table 4, the samples Nos. 101 to 112 having matrices of copper, tin, nickel and aluminum exhibited high friction coefficients and small abrasion loss values of the friction materials and the counterparts. It is also understood that the samples Nos. 101 to 112 were sufficient in strength with neither chipping nor cracking on the appearances after the test.
On the other hand, the samples Nos. 113 to 125, similarly having matrices of copper, tin, nickel and aluminum, were insufficient as friction materials as described below:
The sample No. 113 containing silica in a ratio smaller than those of the remaining samples exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 114 containing silica in a high ratio removed not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, which was remarkably abraded.
The sample No. 115 containing graphite in a ratio smaller than those of the remaining samples exhibited high abrasion loss. The sample No. 116 containing graphite in a high ratio was remarkably reduced in material strength and increased in abrasion loss.
The sample No. 117 containing potassium titanate in a ratio smaller than those of the remaining samples remarkably abraded the counterpart and had an insufficient effect of suppressing abrasion of the counterpart. The sample No. 118 containing potassium titanate in a ratio larger than those of the remaining samples was reduced in material strength and increased in abrasion loss.
The sample No. 119 containing silica in a grain size smaller than those of the remaining samples was incapable of removing an oxide film or the like adhering to the surface of the counterpart and exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 120 containing silica in a grain size larger than those of the remaining samples removed not only an oxide film adhering to the surface of the counterpart but also the counterpart itself, which was remarkably abraded.
The sample No. 121 containing graphite in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and deteriorated in abrasion resistance. The sample No. 122 containing graphite in a grain size larger than those of the remaining samples was incapable of ensuring a homogeneous dispersed state and obtaining a stable friction coefficient due to remarkable segregation of graphite, and increased in abrasion loss.
The samples Nos. 123 to 125 of conventional sintered friction materials containing no potassium titanate exhibited insufficient effects of suppressing abrasion of the counterparts with remarkable abrasion loss of the counterparts due to the absence of potassium titanate.
(TEST EXAMPLE 3)
Mixed powder materials were prepared by blending matrices, dolomite, graphite and potassium titanate in the ratios shown in Table 5, molded into green compacts under a pressure of 2 to 5 tons/cm.sup.2 and thereafter sintered in an N.sub.2 atmosphere at 750.degree. C. for 20 to 90 minutes, thereby preparing samples Nos. 201 to 225 of sintered friction materials.
TABLE 5__________________________________________________________________________ Matrix Potassium Titanate Total Dolomite Graphite Total Ratio Ratio Ratio RatioSample (Vol. (Vol. Grain Size (Vol. Grain Size (Vol.No. Classification Cu Sn Ni Al %) %) (.mu.m) %) (.mu.m) Whiskery Platy Spherical %)__________________________________________________________________________201 inventive 23 3 10 2 38 14 0.5.about.200 30 200.about.500 0 0 18 18202 inventive 23 3 10 2 38 2 0.5.about.200 45 200.about.500 0 0 15 15203 inventive 23 3 10 2 38 8 0.5.about.200 26 200.about.500 0 0 28 28204 inventive 23 3 10 2 38 14 0.5.about.200 20 200.about.500 0 0 28 28205 inventive 26 3.4 11.3 2.3 43 14 0.5.about.200 15 200.about.500 0 0 28 28206 inventive 24.8 3.2 10.8 2.2 41 14 0.5.about.200 40 200.about.500 0 0 5 5207 inventive 24.8 3.2 10.8 2.2 41 14 0.5.about.200 30 200.about.500 0 0 15 15208 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.500 0 0 14 14209 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.500 0 14 0 14210 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.500 14 0 0 14211 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.500 0 7 7 14212 inventive 23 3 10 2 38 8 0.5.about.200 40 200.about.500 7 0 7 14213 comparative 23 3 10 2 38 0.5 0.5.about.200 43 200.about.500 0 0 18.5 18.5214 comparative 23 3 10 2 38 18 0.5.about.200 33 200.about.500 0 0 11 11215 comparative 33.3 4.3 14.5 2.9 55 15 0.5.about.200 5 200.about.500 0 0 25 25216 comparative 22.4 2.9 9.7 2.0 37 2 0.5.about.200 55 200.about.500 0 0 6 6217 comparative 23 3 10 2 38 15 0.5.about.200 44 200.about.500 0 0 3 3218 comparative 23 3 10 2 38 5 0.5.about.200 25 200.about.500 0 0 32 32219 comparative 23 3 10 2 38 8 0.01.about.0.4 40 200.about.500 0 0 14 14220 comparative 23 3 10 2 38 8 220.about.400 40 200.about.500 0 0 14 14221 comparative 23 3 10 2 38 8 0.5.about.200 40 0.1.about.8 0 0 14 14222 comparative 23 3 10 2 38 8 0.5.about.200 40 1200.about.2000 0 0 14 14223 comparative 27 4 12 3 46 14 0.5.about.200 40 200.about.500 0 0 0 0224 comparative 26 3.4 11.3 2.3 43 14 0.5.about.200 43 200.about.500 0 0 0 0225 comparative 24.8 3.2 10.8 2.2 41 14 0.5.about.200 45 200.about.500 0 0 0 0__________________________________________________________________________
A general performance test was made on the samples in accordance with the JASO C406-82 passenger car braking device dynamometer test method. The ranges of friction coefficients were measured at initial braking speeds of 50 km/h and 100 km/h and deceleration of 0.1 to 0.9 G in a second effectiveness test. Abrasion loss values of the samples were measured before and after the general performance test. Further, bending test pieces were collected from the respective samples for performing a three-point bending test under conditions shown in Table 6. Table 7 shows the results. Referring to Tables 5 and 7, the samples Nos. 201 to 212 are inventive samples, and the samples Nos. 213 to 225 are comparative samples. In the columns of "Classification", "inventive" and "comparative" indicate the inventive and comparative samples respectively.
TABLE 6______________________________________ 7 (width) by 5 (thickness)Dimensions of Test Piece (mm) by 30 (length)______________________________________Distance between Support Points (mm) 20Load System three-point bendingCrosshead Speed (mm/min.) 0.5______________________________________
TABLE 7______________________________________ Abra- sion Loss ofSam- Friction Friction Bendingple Classi- Coeffi- Material Appearance after StrengthNo. fication cient (mm) Friction Test (Mpa)______________________________________201 inventive 0.47.about.0.54 0.12 excellent with neither at least chipping nor cracking 40202 inventive 0.44.about.0.50 0.09 excellent with neither at least chipping nor cracking 40203 inventive 0.46.about.0.53 0.13 excellent with neither at least chipping nor cracking 40204 inventive 0.48.about.0.55 0.14 excellent with neither at least chipping nor cracking 40205 inventive 0.48.about.0.55 0.15 excellent with neither at least chipping nor cracking 40206 inventive 0.48.about.0.53 0.10 excellent with neither at least chipping nor cracking 40207 inventive 0.48.about.0.53 0.12 excellent with neither at least chipping nor cracking 40208 inventive 0.46.about.0.51 0.10 excellent with neither at least chipping nor cracking 40209 inventive 0.46.about.0.51 0.10 excellent with neither at least chipping nor cracking 40210 inventive 0.46.about.0.51 0.10 excellent with neither at least chipping nor cracking 40211 inventive 0.46.about.0.51 0.10 excellent with neither at least chipping nor cracking 40212 inventive 0.46.about.0.51 0.10 excellent with neither at least chipping nor cracking 40213 compar- 0.20.about.0.27 0.25 excellent with neither at least ative chipping nor cracking 40214 compar- 0.45.about.0.53 0.22 corner chipped 15 ative215 compar- 0.40.about.0.47 1.10 excellent with neither at least ative chipping nor cracking 40216 compar- 0.30.about.0.40 0.95 corner chipped 10 ative217 compar- 0.45.about.0.50 0.20 corner chipped 24 ative218 compar- 0.46.about.0.52 0.80 corner chipped 26 ative219 compar- 0.18.about.0.25 0.25 excellent with neither at least ative chipping nor cracking 40220 compar- 0.45.about.0.56 0.20 corner chipped 10 ative221 compar- 0.44.about.0.52 0.50 corner chipped 8 ative222 compar- 0.33.about.0.55 0.60 corner chipped 10 ative223 compar- 0.48.about.0.56 0.26 corner chipped 26 ative224 compar- 0.48.about.0.55 0.24 corner chipped 24 ative225 compar- 0.48.about.0.53 0.22 corner chipped 22 ative______________________________________
As understood from Table 7, the samples Nos. 201 to 212 having matrices of copper, tin, nickel and aluminum exhibited high friction coefficients and had neither chipping nor cracking on the appearances after the test. It is also understood that the samples Nos. 201 to 212 maintained a bending strength of at least 40 MPa and had sufficient strength for serving as friction materials.
On the other hand, the samples Nos. 213 to 225, similarly having matrices of copper, tin, nickel and aluminum, were insufficient as friction materials as described below:
The sample No. 213 containing dolomite in a ratio smaller than those of the remaining samples exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 214 containing dolomite in a high ratio was inhibited from sintering of the matrix and reduced in material strength.
The sample No. 215 containing graphite in a ratio smaller than those of the remaining samples exhibited high abrasion loss. The sample No. 216 containing graphite in a high ratio was remarkably reduced in material strength and increased in abrasion loss.
The sample No. 217 containing potassium titanate in a ratio smaller than those of the remaining samples was reduced in material strength with no effect of maintaining the material strength. The sample No. 218 containing potassium titanate in a ratio larger than those of the remaining samples was reduced in material strength and increased in abrasion loss.
The sample No. 219 containing dolomite in a grain size smaller than those of the remaining samples was incapable of removing an oxide film or the like adhering to the surface of the counterpart and exhibited an insufficient friction coefficient for serving as a friction material. The sample No. 220 containing dolomite in a grain size larger than those of the remaining samples was inhibited from sintering of the matrix and reduced in material strength.
The sample No. 221 containing graphite in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and deteriorated in abrasion resistance. The sample No. 222 containing graphite in a grain size larger than those of the remaining samples was incapable of ensuring a homogeneous dispersed state due to remarkable segregation of the graphite, reduced in material strength and increased in abrasion loss.
The samples Nos. 223 to 225 of conventional sintered friction materials containing no potassium titanate exhibited did not exhibit an effect of maintaining material strength and were reduced in material strength and suffered increased abrasion loss due to the absence of potassium titanate.
(TEST EXAMPLE 4)
Mxed powder materials were prepared by blending matrices, orthoclase, graphite and potassium titanate in the ratios shown in Table 8, molded into green compacts under a pressure of 2 to 5 tons/cm.sup.2 and thereafter sintered in an N.sub.2 atmosphere at 750.degree. C. for 20 to 90 minutes, thereby preparing samples Nos. 301 to 325 of sintered friction materials.
TABLE 8__________________________________________________________________________ Matrix Potassium Titanate Total Orthoclase Graphite Total Ratio Ratio Ratio RatioSample (Vol. (Vol. Grain Size (Vol. Grain Size (Vol.No. Classification Cu Sn Ni Al %) %) (.mu.m) %) (.mu.m) Whiskery Platy Spherical %)__________________________________________________________________________301 inventive 23 3 10 2 38 12 0.5.about.180 30 200.about.600 0 0 20 20302 inventive 23 3 10 2 38 4 0.5.about.180 45 200.about.600 0 0 13 13303 inventive 23 3 10 2 38 8 0.5.about.180 26 200.about.600 0 0 28 28304 inventive 23 3 10 2 38 13 0.5.about.180 21 200.about.600 0 0 28 28305 inventive 26 3.4 11.3 2.3 43 13 0.5.about.180 16 200.about.600 0 0 28 28306 inventive 24.8 3.2 10.8 2.2 41 13 0.5.about.180 41 200.about.600 0 0 5 5307 inventive 24.8 3.2 10.8 2.2 41 13 0.5.about.180 31 200.about.600 0 0 15 15308 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 0 14 14309 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 14 0 14310 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 14 0 0 14311 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 7 7 14312 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 7 0 7 14313 comparative 23 3 10 2 38 0.5 0.5.about.180 43 200.about.600 0 0 18.5 18.5314 comparative 23 3 10 2 38 18 0.5.about.180 33 200.about.600 0 0 11 11315 comparative 33.3 4.3 14.5 2.9 55 15 0.5.about.180 5 200.about.600 0 0 25 25316 comparative 22.4 2.9 9.7 2.0 37 2 0.5.about.180 55 200.about.600 0 0 6 6317 comparative 23 3 10 2 38 15 0.5.about.180 44 200.about.600 0 0 3 3318 comparative 23 3 10 2 38 5 0.5.about.180 25 200.about.600 0 0 32 32319 comparative 23 3 10 2 38 8 0.01.about.0.4 40 200.about.600 0 0 14 14320 comparative 23 3 10 2 38 8 220.about.400 40 200.about.600 0 0 14 14321 comparative 23 3 10 2 38 8 0.5.about.180 40 0.1.about.8 0 0 14 14322 comparative 23 3 10 2 38 8 0.5.about.180 40 1200.about.2000 0 0 14 14323 comparative 27 4 12 3 46 14 0.5.about.180 40 200.about.600 0 0 0 0324 comparative 26 3.4 11.3 2.3 43 14 0.5.about.180 43 200.about.600 0 0 0 0325 comparative 24.8 3.2 10.8 2.2 41 14 0.5.about.180 45 200.about.600 0 0 0 0__________________________________________________________________________
Test pieces were collected from the respective samples for performing a counterpart attackability test as a determination of judder resistance under a low surface pressure with a constant-speed frictional abrasion tester. Table 9 shows the test conditions. Table 10 shows counterpart attack quantities (abrasion depths from reference surfaces) and abrasion loss values of the friction materials. Referring to Tables 8 and 10, the samples Nos. 301 to 312 are inventive samples, and the samples Nos. 313 to 325 are comparative samples. In the columns of "Classification", "inventive" and "comparative" indicate the inventive and comparative samples respectively.
TABLE 9______________________________________Shape of Friction Surface (mm) 10 .times. 20______________________________________Counterpart FC200Peripheral Speed (m/s) 10Surface Pressure (kgf/cm.sup.2) 1Friction Time (hr) 24Effective Radius of Friction (m) 0.1______________________________________
TABLE 10______________________________________ Counterpart Attack Abrasion Loss ofSample Quantity Friction MaterialNo. Classification (.mu.m) (mm)______________________________________301 inventive not more than 10 0.12302 inventive not more than 10 0.09303 inventive not more than 10 0.13304 inventive not more than 10 0.14305 inventive not more than 10 0.15306 inventive not more than 10 0.10307 inventive not more than 10 0.12308 inventive not more than 10 0.10309 inventive not more than 10 0.10310 inventive not more than 10 0.10311 inventive not more than 10 0.10312 inventive not more than 10 0.10313 comparative 55 0.19314 comparative not more than 10 0.70315 comparative 15 1.10316 comparative 20 0.95317 comparative 14 0.50318 comparative 16 0.81319 comparative not more than 10 0.75320 comparative 105 0.19321 comparative 20 0.50322 comparative 18 0.55323 comparative 20 0.50324 comparative 18 0.55325 comparative 16 0.60______________________________________
As understood from Table 10, the samples Nos. 301 to 312 having matrices of copper, tin, nickel and aluminum were excellent in judder resistance with counterpart attack quantities of not more than 10 .mu.m and exhibited small abrasion loss values of the friction materials.
On the other hand, the samples Nos. 313 to 325, similarly having matrices of copper, tin, nickel and aluminum, were insufficient as friction materials as described below:
The sample No. 313 containing orthoclase in a ratio smaller than those of the remaining samples was insufficient in judder resistance. The sample No. 314 containing orthoclase in a high ratio was inhibited from sintering of the matrix and reduced in material strength, and exhibited high abrasion loss.
The sample No. 315 containing graphite in a ratio smaller than those of the remaining samples exhibited high abrasion loss. The sample No. 316 containing graphite in a high ratio was remarkably reduced in material strength and increased in abrasion loss.
The sample No. 317 containing potassium titanate in a ratio smaller than those of the remaining samples was reduced in material strength and increased in abrasion loss. The sample No. 318 containing potassium titanate in a ratio larger than those of the remaining samples was reduced in material strength and increased in abrasion loss.
The sample No. 319 containing orthoclase in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix and reduced in material strength, and exhibited high abrasion loss. The sample No. 320 containing orthoclase in a grain size larger than those of the remaining samples was insufficiently improved in judder resistance.
The sample No. 321 containing graphite in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and deteriorated in abrasion resistance. The sample No. 322 containing graphite in a grain size larger than those of the remaining samples was incapable of ensuring a homogeneous dispersed state due to remarkable segregation of graphite, reduced in material strength and increased in abrasion loss.
The samples Nos. 323 to 325 of conventional sintered friction materials containing no potassium titanate were reduced in material strength and increased in abrasion loss due to the absence of potassium titanate.
(TEST EXAMPLE 5)
Mixed powder materials were prepared by blending matrices, magnesium oxide, graphite and potassium titanate in the ratios shown in Table 11, molded into green compacts under a pressure of 2 to 5 tons/cm.sup.2 and thereafter sintered in an N.sub.2 atmosphere at 750.degree. C. for 20 to 90 minutes, thereby preparing samples Nos. 401 to 425 of sintered friction materials.
TABLE 11__________________________________________________________________________ Matrix Potassium Titanate Total Magnesium Oxide Graphite Total Ratio Ratio Ratio RatioSample (Vol. (Vol. Grain Size (Vol. Grain Size (Vol.No. Classification Cu Sn Ni Al %) %) (.mu.m) %) (.mu.m) Whiskery Platy Spherical %)__________________________________________________________________________401 inventive 23 3 10 2 38 12 0.5.about.180 30 200.about.600 0 0 20 20402 inventive 23 3 10 2 38 4 0.5.about.180 45 200.about.600 0 0 13 13403 inventive 23 3 10 2 38 8 0.5.about.180 26 200.about.600 0 0 28 28404 inventive 23 3 10 2 38 13 0.5.about.180 21 200.about.600 0 0 28 28405 inventive 26 3.4 11.3 2.3 43 13 0.5.about.180 16 200.about.600 0 0 28 28406 inventive 24.8 3.2 10.8 2.2 41 13 0.5.about.180 41 200.about.600 0 0 5 5407 inventive 24.8 3.2 10.8 2.2 41 13 0.5.about.180 31 200.about.600 0 0 15 15408 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 0 14 14409 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 14 0 14410 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 14 0 0 14411 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 0 7 7 14412 inventive 23 3 10 2 38 8 0.5.about.180 40 200.about.600 7 0 7 14413 comparative 23 3 10 2 38 0.5 0.5.about.180 43 200.about.600 0 0 18.5 18.5414 comparative 23 3 10 2 38 18 0.5.about.180 33 200.about.600 0 0 11 11415 comparative 33.3 4.3 14.5 2.9 55 15 0.5.about.180 5 200.about.600 0 0 25 25416 comparative 22.4 2.9 9.7 2.0 37 2 0.5.about.180 55 200.about.600 0 0 6 6417 comparative 23 3 10 2 38 15 0.5.about.180 44 200.about.600 0 0 3 3418 comparative 23 3 10 2 38 5 0.5.about.180 25 200.about.600 0 0 32 32419 comparative 23 3 10 2 38 8 0.01.about.0.4 40 200.about.600 0 0 14 14420 comparative 23 3 10 2 38 8 220.about.400 40 200.about.600 0 0 14 14421 comparative 23 3 10 2 38 8 0.5.about.180 40 0.1.about.8 0 0 14 14422 comparative 23 3 10 2 38 8 0.5.about.180 40 1200.about.2000 0 0 14 14423 comparative 27 4 12 3 46 14 0.5.about.180 40 200.about.600 0 0 0 0424 comparative 26 3.4 11.3 2.3 43 14 0.5.about.180 43 200.about.600 0 0 0 0425 comparative 24.8 3.2 10.8 2.2 41 14 0.5.about.180 45 200.about.600 0 0 0 0__________________________________________________________________________
A creak test was carried out on the samples in accordance with the JASO C406-82 passenger car braking device dynamometer test method. Table 12 shows the test conditions. Abrasion loss values were measured before and after the creak test. Table 13 shows the ranges of friction coefficients, creak ratios (number of creaking times.div.total number of braking times) and abrasion loss values in the creak test. Referring to Tables 11 and 13, the samples Nos. 401 to 412 are inventive samples, and the samples Nos. 413 to 425 are comparative samples. In the columns of "Classification", "inventive" and "comparative" indicate the inventive and comparative samples respectively.
TABLE 12______________________________________Car Speed (km/h) 30Braking Start 50.fwdarw.80.fwdarw.120.fwdarw.160.fwdarw.200.fwdarw.160.fwdar w.120.fwdarw.80.fwdarw.50Temperature (.degree.C.)Brake Fluid Pressure 5.fwdarw.10.fwdarw.15.fwdarw.20(kgf/cm.sup.2)Number of Cycles 4 cycles of above combinationTotal Number of 144Braking Times______________________________________
TABLE 13______________________________________ Abrasion Loss of FrictionSample Friction MaterialNo. Classification Coefficient (mm) Creak Ratio______________________________________401 inventive 0.47.about.0.54 0.12 not more than 1%402 inventive 0.44.about.0.50 0.09 not more than 1%403 inventive 0.46.about.0.53 0.13 not more than 1%404 inventive 0.48.about.0.55 0.14 not more than 1%405 inventive 0.48.about.0.55 0.15 not more than 1%406 inventive 0.48.about.0.53 0.10 not more than 1%407 inventive 0.48.about.0.53 0.12 not more than 1%408 inventive 0.46.about.0.51 0.10 not more than 1%409 inventive 0.46.about.0.51 0.10 not more than 1%410 inventive 0.46.about.0.51 0.10 not more than 1%411 inventive 0.46.about.0.51 0.10 not more than 1%412 inventive 0.46.about.0.51 0.10 not more than 1%413 comparative 0.35.about.0.42 0.19 30%414 comparative 0.45.about.0.53 0.62 not more than 1%415 comparative 0.40.about.0.47 1.10 10%416 comparative 0.30.about.0.40 0.95 5%417 comparative 0.45.about.0.50 0.50 5%418 comparative 0.46.about.0.52 0.81 4%419 comparative 0.33.about.0.40 0.65 not more than 1%420 comparative 0.45.about.0.56 0.19 21%421 comparative 0.44.about.0.52 0.50 2%422 comparative 0.33.about.0.55 0.55 6%423 comparative 0.48.about.0.56 0.70 10%424 comparative 0.48.about.0.55 0.65 6%425 comparative 0.48.about.0.53 0.60 5%______________________________________
As understood from Table 13, the samples Nos. 401 to 412 having matrices of copper, tin, nickel and aluminum exhibited high friction coefficients and small abrasion loss. It is also understood that the samples Nos. 401 to 412 had sufficient creak resistance for serving as friction materials with creak ratios of not more than 1%.
On the other hand, the samples Nos. 413 to 425, similarly having matrices of copper, tin, nickel and aluminum, were insufficient as friction materials as described below:
The sample No. 413 containing magnesium oxide in a ratio smaller than those of the remaining samples was insufficiently improved in creak resistance. The sample No. 414 containing magnesium oxide in a high ratio was inhibited from sintering of the matrix, reduced in material strength and increased in abrasion loss.
The sample No. 415 containing graphite in a ratio smaller than those of the remaining samples exhibited high abrasion loss. The sample No. 416 containing graphite in a high ratio was remarkably reduced in material strength and increased in abrasion loss.
The sample No. 417 containing potassium titanate in a ratio smaller than those of the remaining samples was reduced in material strength and increased in abrasion loss. The sample No.418 containing potassium titanate in a ratio larger than those of the remaining samples was reduced in material strength and increased in abrasion loss.
The sample No. 419 containing magnesium oxide in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and increased in abrasion loss. The sample No. 420 containing magnesium oxide in a grain size larger than those of the remaining samples was insufficiently improved in creak resistance.
The sample No. 421 containing graphite in a grain size smaller than those of the remaining samples was inhibited from sintering of the matrix, reduced in material strength and deteriorated in abrasion resistance. The sample No. 422 containing graphite in a grain size larger than those of the remaining samples was incapable of ensuring a homogeneous dispersed state due to remarkable segregation of graphite, reduced in material strength and increased in abrasion loss.
The samples Nos. 423 to 425 of conventional sintered friction materials containing no potassium titanate were reduced in material strength and exhibited remarkable abrasion loss due to the absence of potassium titanate.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Number	Date	Country
9-257860	Sep 1997	JPX
9-336332	Nov 1997	JPX
9-336333	Nov 1997	JPX
9-336334	Nov 1997	JPX
9-342206	Nov 1997	JPX

Number	Date	Country
0316987	May 1989	EPX
57-085876	May 1982	JPX
61-096226	May 1986	JPX
63-280936	Nov 1988	JPX
05032956	Feb 1993	JPX
05247443	Sep 1993	JPX

Sintered friction material

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